JP7687438B2 - Chip-type electronic components - Google Patents

Description

The present invention relates to chip-type electronic components, and in particular to chip-type electronic components containing semiconductor ceramics.

_Some ceramics are known to exhibit a piezoresistance phenomenon in which resistance changes when stress is applied. For example, ceramics such as La1 _{- xSrxMnO3} and _BaTiO3 have a property in which resistance changes depending on the magnitude of strain and stress (piezoresistive effect) (see, for example, Patent Document 1). Perovskite-type manganese oxide La1 _{- xSrxMnO3} exhibits a relatively high piezoresistance effect at room temperature when X=0.25, and resistivity changes by 7% when strained at ₁₅₀ MPa. Also, ceramics such as semiconductor _BaTiO3 exhibit a giant piezoresistance effect.

Patent No. 4611127

In recent years, chip-type electronic components including ceramic bodies have been getting smaller. However, as chip-type electronic components have become smaller, their electrical characteristics have changed before and after reflow mounting. In particular, in the case of chip-type electronic components using semiconductor ceramics, such as positive temperature coefficient (PTC) thermistors using semiconductor _BaTiO3 ceramics, the resistance of the chip-type electronic components has changed significantly before and after reflow mounting.

Therefore, the present invention is directed to chip-type electronic components before reflow mounting, and aims to provide a chip-type electronic component that is configured to suppress significant changes in electrical characteristics after reflow mounting.

According to one aspect of the present invention,
A ceramic body including a semiconductor ceramic made of an oxide including Ti and Ba;
a solid metal electrode formed on an end portion of the ceramic body and in ohmic contact with the ceramic body,
The chip-type electronic component satisfies the following formula (1):
The solid metal electrode has a film stress of 140 MPa or more.

A/V≧3.3 (mm ² /mm ³ )...(1)

Here, A (mm ² ) is the surface area of the solid metal electrode, and V (mm ³ ) is the volume of the ceramic body.

The chip-type electronic components of the present invention can suppress changes in electrical characteristics before and after reflow mounting.

FIG. 1 is a schematic cross-sectional view of a chip-type electronic component according to a first embodiment. FIG. 2 is a schematic partially enlarged cross-sectional view showing one form of the chip-type electronic component according to the first embodiment. FIG. 3 is a schematic partially enlarged cross-sectional view showing another form of the chip-type electronic component according to the first embodiment.

In chip-type electronic components using semiconductor ceramics, such as positive temperature coefficient (PTC) thermistors, the electrical characteristics (e.g., resistance) of the chip-type electronic components before and after reflow mounting can change significantly as the components become smaller.
As a result of extensive research into the cause of such resistance changes, the inventors discovered for the first time that the film stress of the solid metal electrodes formed on the surface of the ceramic body of a chip-type electronic component changes before and after reflow mounting, and that this change in film stress causes the resistance change of the chip-type electronic component. Through further research, the inventors obtained the surprising discovery that by increasing the film stress of the solid metal electrodes to a certain degree in electronic component 10 before reflow mounting, it is possible to keep the rate of resistance change of electronic component 10 before and after reflow mounting low, and thus completed the present invention.

[Embodiment 1]
FIG. 1 is a schematic cross-sectional view of a chip-type electronic component 10 (hereinafter, sometimes simply referred to as "electronic component 10") according to a first embodiment of the present invention.
The electronic component 10 comprises a ceramic body 20 and solid metal electrodes 31 , 41 formed on the ends of the ceramic body 20 .

The ceramic body 20 contains a semiconductor ceramic made of an oxide containing Ti and Ba. The composition of the semiconductor ceramic contains a perovskite type compound containing Ba, Ca, Sr, and Ti as main components, and preferably further contains R (R is at least one selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), Mn, and Si.

The solid metal electrodes 31, 41 are in ohmic contact with the ceramic body 20. In other words, the solid metal electrodes 31, 41 are formed from a solid metal material that can achieve ohmic contact with the ceramic body 20, and are in direct contact with the surface of the ceramic body 20. Suitable solid metal materials that can achieve ohmic contact with the ceramic body 20 include, for example, Cr, NiCr alloys, Al, and Zn-Ag (ohmic Ag).

The electronic component 10 may further include a protective layer covering the solid metal electrodes 31, 41. In the example shown in FIG. 1, the protective layer is composed of four layers: conductive solid metal layers 32, 42, conductive resin layers 33, 43, first plating layers 34, 44, and second plating layers 35, 45. The conductive solid metal layers 32, 42 are disposed between the solid metal electrodes 31, 41 and the conductive resin layers 33, 43. The conductive resin layers 33, 43 are disposed between the conductive solid metal layers 32, 42 and the plating layers (first plating layers 34, 44 and second plating layers 35, 45).

The solid metal electrode 31, the conductive solid metal layer 32, the conductive resin layer 33, the first plating layer 34, and the second plating layer 35 can be considered to constitute the first external electrode 30 of the electronic component 10. Similarly, the solid metal electrode 41, the conductive solid metal layer 42, the conductive resin layer 43, the first plating layer 44, and the second plating layer 45 can be considered to constitute the second external electrode 40 of the electronic component 10.

The electronic component 10 of the present invention satisfies the following formula (1).

A/V≧3.3 (mm ² /mm ³ )...(1)

Here, A (mm ² ) is the surface area of the solid metal electrodes 31 and 41 , and V (mm ³ ) is the volume of the ceramic body 20 .

Equation (1) shows the ratio of the surface area A ( ^mm2 ) of the solid metal electrodes 31, 41 to the volume V ( ^mm3 ) of the ceramic body 20. The smaller the electronic component 10, the larger the value of A/V. Although this varies depending on the area where the solid metal electrodes 31, 41 are formed, for example, in the case of a chip size of 0603 in millimeters, if the solid metal electrodes 31, 41 are formed only on the end faces 21, 22 on both sides of the ceramic body 20, A/V can be approximately 3.3 ^mm2 / ^mm3 .
The volume V (mm ³ ) of the ceramic body 20 and the surface area A (mm ² ) of the solid metal electrodes 31, 41 will be described in detail later.

In the electronic component 10 of the present invention, the film stress of the solid metal electrodes 31, 41 is set to 140 MPa or more before reflow mounting, which makes it possible to suppress the rate of resistance change of the electronic component 10 before and after reflow mounting to a low value (e.g., less than 10%).
The mechanism by which the rate of resistance change can be suppressed by controlling the film stress of the solid metal electrodes 31 and 41 to be high will be described below.

The solid metal electrodes 31, 41, which are in ohmic contact with the ceramic body 20, are in direct contact with the surface of the ceramic body 20. If there is residual stress (film stress) inside the solid metal electrodes 31, 41, the surface portion of the ceramic body 20 is subjected to stress proportional to the magnitude of the film stress.

When the electronic component 10 is reflow mounted, the solid metal electrodes 31, 41 are affected by the heat generated during reflow mounting, causing a change in film stress. This change in film stress changes the stress experienced by the surface layer of the ceramic body 20, and the resistance of the ceramic body 20 changes due to the piezoresistive effect. Although the change in stress experienced by the surface layer of the ceramic body 20 is minute, this stress change becomes apparent as the electronic component 10 is miniaturized, and the change in resistance of the ceramic body 20 becomes noticeable.

The inventors' research has revealed that at typical reflow temperatures (130°C to 300°C), the film stress of the solid metal electrodes 31, 41 is approximately 500 MPa. It has also been found that if the film stress of the solid metal electrodes 31, 41 before reflow mounting is close to 500 MPa, the rate of resistance change before and after reflow mounting is small. From this, the inventors have discovered that by increasing the film stress of the solid metal electrodes 31, 41 in the electronic component 10 before reflow mounting (more specifically, by making it close to the film stress of the solid metal electrodes 31, 41 after reflow mounting), the rate of resistance change before and after reflow mounting can be made extremely small.

However, the film stress of the solid metal electrodes 31, 41 also changes depending on the film formation conditions of the solid metal electrodes 31, 41 (for example, in the case of sputtering, the sputtering temperature, sputtering time, etc.), various processing treatments (for example, barrel polishing, etc.), and preliminary heat treatments. Therefore, the inventors have closely examined the relationship between the resistance change rate that is acceptable for the electronic component 10 and the film stress of the solid metal electrodes 31, 41 before reflow mounting, and have found that if the film stress of the solid metal electrodes 31, 41 before reflow mounting is controlled to 140 MPa or more, the resistance change rate before and after reflow mounting can be suppressed to a range that is acceptable for general use (approximately less than 10%).

The film stress of the solid metal electrodes 31, 41 in the electronic component 10 before reflow mounting can be controlled by adjusting the film formation conditions of the solid metal electrodes 31, 41 (e.g., in the case of sputtering, the sputtering temperature, sputtering time, etc.), the processing of the electronic component 10 (e.g., barrel polishing, etc.), and the conditions of the preliminary heat treatment.

The film stress of the solid metal electrodes 31, 41 is preferably 300 MPa or more, which can further reduce the rate of resistance change before and after reflow mounting.
The film stress of the solid metal electrodes 31, 41 is preferably 490 MPa or less, and the occurrence of cracks or peeling in the solid metal electrodes 31, 41 due to the film stress can be suppressed.
In order to increase the film stress of the solid metal electrodes 31, 41, various manufacturing conditions need to be controlled, which may increase the manufacturing costs of the solid metal electrodes 31, 41, and as a result, may increase the manufacturing costs of the electronic component 10. Therefore, it is more preferable that the film stress is 400 MPa or less, which can suppress an increase in the manufacturing costs of the electronic component 10.

The film stress of the solid metal electrodes 31 and 41 can be measured by the method described in the Examples.
In addition, when a protective layer covering the solid metal electrodes 31, 41 exists, the protective layer is removed to expose the solid metal electrodes 31, 41 before measuring the film stress. The method for removing the protective layers (the conductive solid metal layers 32, 42, the conductive resin layers 33, 43, the first plating layers 34, 44, and the second plating layers 35, 45) is not particularly limited, and includes, for example, physical removal and chemical removal as shown below. Physical removal methods include physical etching and barrel etching. Chemical removal methods include a method of dissolving and removing each layer with a solvent that selectively dissolves each layer. Layers made of metal materials (the first plating layers 34, 44 and the second plating layers 35, 45) can be dissolved with various acids such as hydrochloric acid, nitric acid, ferric chloride, ammonium sulfate, hydrogen peroxide, sulfuric acid, boric acid, cyanide, hydrofluoric acid, and phosphoric acid. Layers containing resin materials (the conductive resin layers 32, 42) can be dissolved and removed with various organic solvents such as aromatics, ketones, and ethers.

Next, the volume V (mm ³ ) of the ceramic body 20 and the surface area A (mm ² ) of the solid metal electrodes 31 and 41 will be described in detail.

The dimensions of ceramic body 20 are "width 20W" (mm) in the W direction, "length 20L" (mm) in the L direction, and "thickness 20T" (mm) (not shown) in the T direction. Using the dimensions of ceramic body 20, the volume V of ceramic body 20 can be determined as follows.

Volume V of ceramic body 20 (mm ³ ): 20W×20T×20L

The volume V of the ceramic body 20 is preferably 0.001 mm ³ or more and 0.12 mm ³ or less. In such a small-sized ceramic body 20, the effect of suppressing the rate of resistance change by controlling the film stress of the solid metal electrodes 31, 41 is remarkable.

Using the dimensions of ceramic body 20 (width 20W, length 20L, and thickness 20T), the area of each of end faces 21, 22 of ceramic body 20 can be determined as follows.

Area of first end face 21 (mm ² ): 20W×20T
Area of second end face 22 (mm ² ): 20W×20T

The surface area A of the solid metal electrodes 31 and 41 means the sum of the entire surfaces of the solid metal electrodes 31 and 41. Figures 2 and 3 show solid metal electrodes 31 and 41 of different shapes, and the surface area A of each of the solid metal electrodes 31 and 41 is described.

Fig. 2 is a schematic partial enlarged cross-sectional view of one end (the side of the first end face 21) of the ceramic body 20 of the electronic component 10 shown in Fig. 1. In Fig. 2, the solid metal electrode 31 covers the first end face 21 of the ceramic body 20 but does not cover the side face 23 of the ceramic body 20. In this case, the surface area A21 of the solid metal electrode 31 is substantially equal to the area of the first end face 21.
Since the area of the first end surface 21 is 20W×20T, the surface area A21 of the solid metal electrode 31 is 20W×20T.

When the solid metal electrode 41 formed at the other end (the side of the second end face 22 shown in Figure 1) of the ceramic body 20 is similar to the solid metal electrode 31 shown in Figure 2 (i.e., when it covers the second end face 22 of the ceramic body 20 but does not cover the side face 23 of the ceramic body 20), the surface area of the solid metal electrode 41 is substantially equal to the area of the second end face 22.
Since the area of the second end surface 22 is 20W×20T, the surface area of the solid metal electrode 41 is 20W×20T.

And since the surface area A of the solid metal electrodes 31, 41 is the sum of the entire surfaces of the solid metal electrodes 31, 41, the surface area A can be calculated as (20W x 20T) + (20W x 20T) = (20W x 20T) x 2.

3 is a schematic partial enlarged cross-sectional view of one end (end face 21 side) of the ceramic body 20 in another form of electronic component 10. In FIG. 3, the solid metal electrode 31 is different from the solid metal electrode 31 shown in FIG. 2 in that it covers not only the first end face 21 of the ceramic body 20 but also a part of the side face 23 of the ceramic body 20 adjacent to the first end face 21. Note that the conductive solid metal layer 32 is not shown in FIG. 3, but the conductive solid metal layer 32 may be formed to cover only the end face of the solid metal electrode 31 (a surface approximately parallel to the first end face 21 of the ceramic body 20) or to cover the end face and the side face (a surface approximately parallel to the side face 23 of the ceramic body 20).

3, the surface area of the solid metal electrode 31 is A31, which is the surface area of a surface approximately parallel to the first end face 21 of the ceramic body 20, and A32, which is the surface area of a surface approximately parallel to the side face 23 of the ceramic body 20. The surface area of the solid metal electrode 31 is the sum of the surface areas A31 and A32. Note that while FIG. 3 shows the solid metal electrode 31 formed on two of the four side faces 23 of the ceramic body 20 (LT faces), the solid metal electrode 31 may also be formed on the remaining two faces (LW faces). In that case, when calculating the surface area of the solid metal electrode 31, the surface area of the solid metal electrode 31 formed on the LW faces must also be added.

When the solid metal electrode 41 formed on the other end of the ceramic body 20 (the side of the second end face 22 shown in Figure 1) is similar to the solid metal electrode 31 shown in Figure 3 (i.e., when it continuously covers not only the second end face 22 of the ceramic body 20 but also a part of the side face 23 of the ceramic body 20 adjacent to the second end face 22), the surface area of the solid metal electrode 41 is the sum of the surface area of the surface approximately parallel to the second end face 22 and the surface area of the surface approximately parallel to the side face 23 of the ceramic body 20, as is the surface area of the solid metal electrode 31 on the first end face 21 side.

The surface area A of the solid metal electrodes 31, 41 can be calculated as the sum of the surface area of the solid metal electrode 31 on the first end face 21 side and the surface area of the solid metal electrode 41 on the second end face 22.

For solid metal electrodes 31, 41 having the shape shown in Figure 3, the dimensions of the solid metal electrodes 31, 41 on each side are measured using a microscope or the like to calculate the surface area.

[Method of manufacturing chip-type electronic component 10]
A method for manufacturing an electronic component 10 according to the first embodiment will be described using a PTC thermistor having the structure shown in FIG. 1 as an example.

(Fabrication of Ceramic Body 20)
The ceramic body 20 is made of a ceramic material in which a specific additive is added to, for example, barium titanate (BaTiO ₃ ). The additive may be, for example, a rare earth. The rare earth to be added is typically selected from Sm, Er, and Y, and may also be selected from Nd, La, etc.

In the preparation of the ceramic body 20, first, a predetermined amount of ceramic raw materials such as _BaCO3 , _TiO2 , PbO, _SrCO3 , _CaCO3 , and a rare earth additive (semiconducting agent) are weighed as the raw materials of the ceramic body. The rare earth additive may be an oxide of at least one rare earth element selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. In addition to the above-mentioned ceramic raw materials and rare earth additive, a property improver such _{as Mn2O3} and a sintering aid such as _SiO2 may be used as the raw materials of the ceramic body. The weighed raw materials are charged into a ball mill together with grinding media such as partially stabilized zirconia (PSZ) (hereinafter also referred to as PSZ balls) and pure water, and wet mixed and ground. The resulting mixture is calcined at a predetermined temperature (e.g., 1000 to 1200° C.) to obtain a calcined powder.

The resulting calcined powder is mixed with an organic binder, dispersant and pure water, then dried to form granules. The resulting granules are molded to obtain a green body. The green body is then degreased and debindered, and fired at a specified temperature (1200-1400°C) in a specified atmosphere to obtain the ceramic body 20A.

(Formation of Solid Metal Electrodes 31, 41)
As shown in Figures 1 to 3, solid metal electrodes 31, 41 are formed so as to cover the ends of the ceramic body 20 (only the end faces 21, 22 as shown in Figures 1 and 2, or the end faces 21, 22 and parts of the side faces 23 as shown in Figure 3).

The solid metal electrodes 31, 41 are formed from a metal material that can make ohmic contact with the ceramic body 20, such as metal materials such as Zn, Ni, Al, Cr, V, and W, alloys of these metals with Ag, and alloy materials such as NiCr. In particular, solid metal materials such as Cr, NiCr alloys, Al, and Zn-Ag (ohmic Ag) are suitable.

The solid metal electrodes 31, 41 can be formed by a known film forming method, such as a sputtering method, a vapor deposition method, a coating method (a conductive paste is applied to a predetermined position and then baked), or a dipping method.
For example, a Cr film, a NiCr alloy film, and an Al film are preferably formed by sputtering, while a Zn--Ag film (ohmic Ag film) is preferably formed by coating and then baking.

(Formation of protective layer)
A protective layer may be formed to cover the solid metal electrodes 31 and 41 .
In the first embodiment, the protective layer is composed of four layers: conductive solid metal layers 32, 42, conductive resin layers 33, 43, first plating layers 34, 44, and second plating layers 35, 45. A method for forming each layer will be described.

(Conductive solid metal layer 32, 42)
The conductive solid metal layers 32, 42 are preferably formed from a solid metal material that has high adhesion to the solid metal electrodes 31, 41 and high weather resistance. Examples of the solid metal material include metal materials such as Ni, Cr, Au, Ag, and W, and alloy materials such as NiCr, NiCu, and NiV. As the conductive solid metal layers 32, 42, solid metal material films such as NiCu alloy films, NiV alloy films, and Ag films are particularly preferred.

The conductive solid metal layers 32, 42 may be formed from the same material as the solid metal electrodes 31, 41. For example, if the solid metal material that can obtain ohmic properties with the ceramic body 20 has the characteristics required for the solid metal material that forms the protective layer (conductive solid metal layers 32, 42), the conductive solid metal layers 32, 42 and the solid metal electrodes 31, 41 may be formed from the same material. If they are formed from the same material, the solid metal electrodes 31, 41 and the conductive solid metal layers 32, 42 can be provided as a single layer in an integrated manner.

The conductive solid metal layers 32, 42 are composed of a single layer or a multilayer film, and can be formed by a known film formation method. For example, a sputtering method, a vapor deposition method, a coating method (a conductive paste is applied to a predetermined position and then baked), a dipping method, etc. can be used. For example, a NiCu alloy film, a NiV alloy film, and an Ag film are preferably formed by a sputtering method.

(Formation of conductive resin layers 33, 43)
The conductive resin layers 33, 43 are provided by hardening a resin electrode paste having fluidity. The resin electrode paste contains a conductive powder and a resin raw material. The resin electrode paste is applied to the ends of the ceramic body 20 so as to cover the solid metal electrodes 31, 41, and then the resin raw material in the resin electrode paste is hardened.
As the conductive powder contained in the resin electrode paste, metal powders such as Ag, Au, Ni, Cu, Pt, Pd and Al can be used.
Examples of the resin raw material contained in the resin electrode paste that can be used include epoxy resin, phenol resin, urethane resin, silicone resin, and polyimide resin.

(Formation of first plating layers 34, 44 and second plating layers 35, 45)
A plating layer (first plating layer 34 and second plating layer 35) is formed so as to cover the surfaces of the conductive resin layers 33, 43. The plating layer preferably has a multi-layer structure including the first plating layer 34, 44 in contact with the conductive resin layers 33, 43 and the second plating layer 35, 45 covering the first plating layer 34, 44. In this case, after the first plating layer 34, 44 is formed so as to cover the surfaces of the conductive resin layers 33, 43, the second plating layer 35, 45 is formed so as to cover the first plating layer 34, 44.

The first plating layers 34, 44 can be formed, for example, by electrolytic plating of at least one of Ni and Cu. The second plating layers 35, 45 can be formed, for example, by electrolytic plating of Sn. The first plating layers 34, 44 and the second plating layers 35, 45 can be formed by a known plating method, for example, barrel plating using a ball.

Above, the manufacturing method for the chip-type electronic component 10 according to embodiment 1 of the present invention has been explained using a PTC thermistor as an example, but other chip-type electronic components can also be manufactured as appropriate based on the description in this specification.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

The measurement samples were prepared according to the following procedure. Approximately 5,000 measurement samples can be formed in one production run.
The film stress of the solid metal electrode in each measurement sample was adjusted to the film stress shown in Table 1 by adjusting the film formation conditions of the solid metal electrode, the barrel polishing conditions, the preliminary heat treatment conditions, etc.

(Examples 1 to 5, Comparative Examples 2 and 3)
The ceramic body 20 was prepared by grinding and mixing the raw materials of the ceramic body 20, calcining, molding, firing, and cutting. The raw materials were ground and mixed by mixing BaCO ₃ , CaCO ₃ , SrCO ₃ , PbO, TiO ₂ as main components, Sm ₂ O ₃ as a rare earth element, MnO ₂ as a property adjusting material, and SiO ₂ as a sintering aid in a predetermined amount, grinding, and drying. The obtained dried powder was calcined at a maximum temperature of 1200°C in an air atmosphere. The obtained calcined powder was mixed with an organic binder, a dispersing agent, and pure water, mixed, and then dried to be granulated. The obtained granulated material was compression molded. The molded body was subjected to a degreasing process and a debinding process, and then fired at a maximum temperature of 1380°C. The fired body was cut to a predetermined size to obtain the ceramic body 20.

Solid metal electrodes 31, 41 (Cr films) and conductive solid metal layers 32, 42 (multilayer films of NiCu alloy film and Ag film) were formed in this order so as to cover only both end faces 21, 22 of the ceramic body 20. Each film was formed by sputtering. CS-S manufactured by ULVAC was used as the sputtering device, and the film thickness was adjusted by flowing argon gas at an absolute pressure of less than 1 Pa, a sputtering output of 200 W, and adjusting the sputtering time depending on the film type.
Table 1 shows the types of materials used for the solid metal electrodes 31 and 41 in the examples and comparative examples, and the film thicknesses of the solid metal electrodes 31 and 41.

(Example 6, Comparative Example 1)
The solid metal electrodes 31, 41 were formed by a dipping method so as to cover only the end faces 21, 22 of the ceramic body 20 prepared in the same manner as in Example 1. The end face 21 of the ceramic body 20 was immersed in a paste containing Ag-Zn, coated with the paste, and dried at 180°C, and the end face 22 was similarly immersed, coated, and dried to obtain a dried body having an Ag-Zn film (ohmic Ag film) formed on both end faces. The dried body was passed through a belt furnace with a maximum temperature of 600°C to bake the solid metal electrodes 31, 41 onto the ceramic body 20. The film thicknesses of the solid metal electrodes 31, 41 used in each of Example 6 and Comparative Example 1 are shown in Table 1.

The ceramic substrate 20 used in Examples 1 to 6 and Comparative Examples 1 to 3 had a square prism shape and the following dimensions (corresponding to a 0603 chip).

Length 20L: 0.60mm
Width 20W: 0.28mm
・Thickness 20T: 0.28 mm

Since the solid metal electrodes 31, 41 were formed only on both end faces 21, 22 (corresponding to the WT faces) of the ceramic body 20, the surface area A ( ^mm2 ) of the solid metal electrodes 31, 41 was (20W x 20T) x 2 = (0.28 mm x 0.28 mm) x 2 = 0.1568 ^mm2 .
The volume V (mm ³ ) of the ceramic body 20 was 20W×20T×20L=0.28 mm×0.28 mm×0.60 mm=0.04704 mm ³ .
From these values, A/V was calculated and is shown in Table 1.

(Measurement of film stress)
The film stress of the solid metal electrode was measured by the sin ² ψ-2θ method using X-ray diffraction, which is an excellent measurement method in terms of high reproducibility.
As the XRD diffraction device, a micro X-ray diffraction device can be used. In the embodiment, a D8 DISCOVER manufactured by BRUKER axs was used. CuKα rays were used as the X-ray source.
In each of the examples and comparative examples, three samples were randomly selected from the approximately 5,000 measurement samples produced, and were subjected to measurement.

The sin ² ψ method using a micro X-ray diffractometer is a method for determining the film stress by measuring a specific diffraction peak. The specific diffraction peak is selected as follows.
Select one diffraction peak from "any crystal plane" of "a certain crystal phase." In order to confirm the amount of strain while tilting the measurement sample, it is desirable to select a diffraction peak on the high-angle side that is sensitive to the strain of the crystal phase, and a diffraction peak that does not overlap with the diffraction peaks of other crystal planes and has a clear peak top that is an index of the interplanar spacing (i.e., has a strong intensity).

In the examples and comparative examples, the diffraction lines of Cr(220) were measured for the Cr film, NiCr(222) for the NiCr alloy film, and Ag(222) for the ohmic Ag electrode.

The film stress of the solid metal electrode is calculated from the following formula (2).

σ=K・∂(2θ)/∂(sin ² ψ)...(2)

Here, K is a stress constant, which is calculated by the following formula (3).

K=E/ν...(3)

Here, E is the Young's modulus of the material constituting the solid metal electrode, and ν is the Poisson's ratio of the material constituting the solid metal electrode.

When determining the membrane stress in the examples and comparative examples, the following values were used for Young's modulus E and Poisson's ratio v. These values are publicly known values described in the Scientific Annals, various literature, etc.
NiCr alloy: E/ν=29400MPa/0.21
Cr:E/ν=82700MPa/0.367
Ohmic Ag: E/ν=214000 MPa/0.31
The film stress of the solid metal electrode of the measurement sample was calculated from the results of the micro X-ray diffraction. The average film stress value obtained from the three measurement samples was calculated and is shown in Table 1 under "Film stress of solid metal electrode."

(Evaluation of Resistance Change Rate)
In order to simulate reflow mounting, the measurement sample was placed in a thermostatic chamber at 230°C for 30 minutes. The resistance of the measurement sample before pseudo mounting (before heat treatment) and after pseudo mounting (after heat treatment) was measured, and the rate of change in resistance after heating relative to the resistance before heating (resistance change rate) was measured. First, the room temperature resistance value of the sample before pseudo mounting (before heat treatment) was measured. Next, the sample was mounted on a mounting board using solder paste, and pseudo mounting (heat treatment) was performed. The room temperature resistance value of the sample after pseudo mounting (after heat treatment) was measured.

A glass epoxy resin board (FR-4) was used as the mounting board, and Sn-3.0Ag-0.5Cu M705-GRN360-K2KJ-V manufactured by Senju Metal Industry Co., Ltd. was used as the solder paste. A commercially available digital multimeter was used as the resistance measuring device. In the examples, an R6451A digital multimeter manufactured by ADVANTEST was used, but similar measurement results can be obtained with other digital multimeters. For the resistance measurement, the digital multimeter was placed in contact with both electrodes (positive and negative) of the sample before pseudo-mounting, and the digital multimeter was placed in contact with the board wiring for the sample after pseudo-mounting.

Ten samples were randomly selected from the approximately 5,000 measurement samples produced, and were subjected to measurement. For each sample, the pre-mounting resistance Ri and the post-mounting resistance Rf were measured, and the resistance change rate was calculated using the following formula (4).

Resistance change rate (%)=(Rf/Ri−1)×100 (4)

The resistance change rate was determined for each of the 10 measurement samples, and the average value was calculated and shown in Table 1 under "Resistance change rate."

In Examples 1 to 6, in which the film stress of the solid metal electrode before heat treatment was 140 MPa or more, the resistance change rate after heat treatment was less than 10%. On the other hand, in Comparative Examples 1 to 3, in which the film stress of the solid metal electrode before heat treatment was less than 140 MPa, the resistance change rate after heat treatment was 10% or more.

This application claims priority to Patent Application No. 2021-197184, filed in Japan on December 3, 2021, the entire contents of which are incorporated herein by reference.

REFERENCE SIGNS LIST 10 Chip-type electronic component 20 Ceramic body 21, 22 End face of ceramic body 23 Side face of ceramic body 30, 40 External electrode 31, 41 Solid metal electrode 32, 33 Conductive solid metal layer 33, 43 Conductive resin layer 34, 44 First plating layer 35, 45 Second plating layer

Claims (6)

A ceramic body including a semiconductor ceramic made of an oxide including Ti and Ba;
a solid metal electrode formed on an end portion of the ceramic body and in ohmic contact with the ceramic body,
The chip-type electronic component satisfies the following formula (1):
A chip-type electronic component, wherein the solid metal electrode has a film stress of 140 MPa or more.

A/V≧3.3 (mm ² /mm ³ )...(1)

Here, A (mm ² ) is the surface area of the solid metal electrode, and V (mm ³ ) is the volume of the ceramic body.
The chip-type electronic component according to claim 1, wherein the film stress of the solid metal electrode is 490 MPa or less. 3. The chip-type electronic component according to claim 1, wherein the ceramic body has a volume V of 0.001 ^mm3 or more and 0.12 ^mm3 or less. 3. The chip-type electronic component according to claim 1 , wherein the solid metal electrodes cover end faces of the ceramic body. The chip-type electronic component according to claim 4, wherein the solid metal electrode continuously covers the end face of the ceramic body to a portion of the side face of the ceramic body adjacent to the end face. 3. The chip-type electronic component according to claim 1 or 2, wherein the composition of the semiconductor ceramic contains a perovskite compound containing Ba, Ca, Sr, and Ti as main components, and further contains R (R is at least one selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), Mn, and Si.

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